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Topic Review (Newest First)

03-11-2013 08:23 AM

BOBCRMAN@aol.com

Building pump gas engines to make power, using antiquated parts and methods is a serious challenge. This is why we don't do it. The ONLY things we "keep" are the block, crank and head castings. Everything else gets changed, including the rod length (if a "racer").

Taking the "dome" off a piston and updating the heads and using a modern cam grind, is daily proceedure around most good shops these days.

I agree. I am also a fan of the 396. Raced them "back in the day".
The problem I have is I've been there and tend to be a realist.

I see guys with great expectations and little experience trying to build these motors. Because their grandpa or buddies say it is the great way to go. GM did a good job advertising the SS396! Still in peoples' heads.

Compression is major problem. To build compression you need tall dome or small combustion chamber. Tall dome conflicts with flame travel/power. Small chambers are not really available bolt on aftermkt and the old stock stuff doesn't flow air. Plus the small bore shrouding really screws up the air flow into cylinders. Especially on the two bad cylinders on each side of a BBC.
Then to get decent valve lift, the piston valve reliefs have to be cut, thus lowering all important compression ratio.

It may rub some people wrong but the facts are there. If you want horsepower on a "reasonable" budget. Pass on the small bore BBC.

03-11-2013 07:53 AM

Mr. P-Body

Well, I guess it doesn't mean much, experience... It takes a LOT more than 375 HP to move a 3,500 lb. car into the 11s. NOT an opinion, a mathematical fact. My '70 GTO ran 13.60s "stock" (@ Orange County, 1973). It was a "Ram, Air" car. No 396 of any description ever beat it in a race while I was in it, including at least 5 "375 HP" versions. Never saw a real L-78 (425 HP) "in person" (VERY RARE). When Rick Holladay first broke into the 10s (10.80s, pump gas, TriPower 434), he dynoed 435 RWHP, which is well over 550 at the crankshaft (GBHP).

Building pump gas engines to make power, using antiquated parts and methods is a serious challenge. This is why we don't do it. The ONLY things we "keep" are the block, crank and head castings. Everything else gets changed, including the rod length (if a "racer").

Taking the "dome" off a piston and updating the heads and using a modern cam grind, is daily proceedure around most good shops these days.

Jim

03-10-2013 11:52 PM

hotrod937

Quote:

Originally Posted by painted jester

If you build the 396 you would have to spin the motor a little tighter and run a little more cam and compression to bridge the 454s advantage in cu inch and Torque!

The 396 has had a big reduction in the cost of its parts. A forged 396 crank sells for about $100, A forged crank for a 454 could cost as much as $400 , And a used 396 short-block will usually only set you back less than $300. While a 454 short-block would cost $600 . You already have the 396 so you can put the 454 money into your little RAT build, and with a 450 to 500 HP 396 that revs 7500 RPM , put the 454 boat anchor back on the chain and in the water! Its not that hard!

After building and running 409s, I owned and built many 396s & 427s mainly blue printed & balanced stock 396/375 HP & 396/425 HP & 427/425 HP high revers that when built just about dyno'd at 450 & over 500 HP. And that's stock blue printing and good balancing! A little porting ,and L 88 cams(L-88, 264/270, 112/108, .560"/.580" lift) or the ZL-1, 262/273, 110/?, .560"/.600" lift) but there are much better solid roller cams now, and intake & carb work, I don't have much experience with the 396/325 HP builds except for numbers matching restorations a few street rod minor hop ups! but installing splayed-bolt caps like P-Body said cures the main problem!

If a 454 is good why not a 496

Mr. P-Body, And I both seem to like 396s & 427s LOL we're probably a dieing breed just like the "Little Big Block 396s" I think the heads you have would keep your compression up and with the stock pistons the compression was around 10.5 to one, a little milling, a deck shave, a thinner head gasket and 11 to 11.5 is possible, do your own porting, a ZL1 cam or solid roller, Roller rockers, lighten the valve train, balance the reciprocating assembly, etc and 420 HP is reachable!

Better heads (aluminum) & pistons for Higher compression (13to1), bigger cam and 500 hp can be achieved but fuel requirements will be hard to feed on the street!

Why did you pick the figure of 500 HP for the 396? AP was right about its more easily obtainable with the 454 (and on pump gas)! The 396 /425 HP little rat when you put your foot in it would;> Still Snap your head into the back seat<

Jester

Good info. I explain everything at the top. If I can make a sbc with 490hp then why can't I make a bbc have 550?

03-07-2013 10:20 PM

vinniekq2

seems to me the 360 hp was also way under rated
for anyone that thinks a 396 is not easy to make power,I hope you are not one of those same people that think the 383 stroker small block is a street killer? The 396 has more potential by a long stretch

03-07-2013 10:07 PM

painted jester

I forgot to mention LOL Many don't know that the 375 HP and 425HP 396s were internally identical it was the exhaust system of the model it was installed in that made a difference in HP!

Jester

03-07-2013 08:27 PM

painted jester

If you build the 396 you would have to spin the motor a little tighter and run a little more cam and compression to bridge the 454s advantage in cu inch and Torque!

The 396 has had a big reduction in the cost of its parts. A forged 396 crank sells for about $100, A forged crank for a 454 could cost as much as $400 , And a used 396 short-block will usually only set you back less than $300. While a 454 short-block would cost $600 . You already have the 396 so you can put the 454 money into your little RAT build, and with a 450 to 500 HP 396 that revs 7500 RPM , put the 454 boat anchor back on the chain and in the water! Its not that hard!

After building and running 409s, I owned and built many 396s & 427s mainly blue printed & balanced stock 396/375 HP & 396/425 HP & 427/425 HP high revers that when built just about dyno'd at 450 & over 500 HP. And that's stock blue printing and good balancing! A little porting ,and L 88 cams(L-88, 264/270, 112/108, .560"/.580" lift) or the ZL-1, 262/273, 110/?, .560"/.600" lift) but there are much better solid roller cams now, and intake & carb work, I don't have much experience with the 396/325 HP builds except for numbers matching restorations a few street rod minor hop ups! but installing splayed-bolt caps like P-Body said cures the main problem!

If a 454 is good why not a 496

Mr. P-Body, And I both seem to like 396s & 427s LOL we're probably a dieing breed just like the "Little Big Block 396s" I think the heads you have would keep your compression up and with the stock pistons the compression was around 10.5 to one, a little milling, a deck shave, a thinner head gasket and 11 to 11.5 is possible, do your own porting, a ZL1 cam or solid roller, Roller rockers, lighten the valve train, balance the reciprocating assembly, etc and 420 HP is reachable!

Better heads (aluminum) & pistons for Higher compression (13to1), bigger cam and 500 hp can be achieved but fuel requirements will be hard to feed on the street!

Why did you pick the figure of 500 HP for the 396? AP was right about its more easily obtainable with the 454 (and on pump gas)! The 396 /425 HP little rat when you put your foot in it would;> Still Snap your head into the back seat<

Jester

03-07-2013 06:35 PM

ap72

Quote:

Originally Posted by Mr. P-Body

Here I go again, "against the grain"... We get "flack" all the time for building "baby big blocks". I like 396. It's a good, solid basis. I shares the rod/stroke ratio with 427, and revs just as nicely.

I believe the heads you have with the 325 HP version, have fairly good sized oval intake ports, at least "better" than most mid-70s and later oval ports. The "closed" chamber makes things a LITTLE tougher, but not a big deal. Icon makes a nice replacement piston that's lighter than the Speed Pro, and you can still machine the dome to "fit". Both the Icon and Speed Pro are readily available and up to the task.

We install the 2.190/1.88" valves in the oval port heads all the time. A little "blending" in the bowls is all that's really needed, and they can "feed" a 396 well over 7,000.

So, yes, 396 can be a very potent street engine. And no, you don't need the monster money parts to do it.

BTW: All 366s, 396s and 427s used the 6223 crankshaft. Good forging. I don't believe you need a 4-bolt until power exceeds 600 HP or RPM exceeds 7,500. Then, installing splayed-bolt caps to your existing block would be infinitely more desirable than trying to find a 375 or 425 HP block...

Jim

Those et's would indicate that recipe is good for around 375hp, which is about right for a bunch of cheap left over parts on a 396. And there's not a damn thing wrong with that, BUT its well short of the 500hp goal originally indicated.

03-07-2013 05:52 PM

Mr. P-Body

Here I go again, "against the grain"... We get "flack" all the time for building "baby big blocks". I like 396. It's a good, solid basis. I shares the rod/stroke ratio with 427, and revs just as nicely.

I believe the heads you have with the 325 HP version, have fairly good sized oval intake ports, at least "better" than most mid-70s and later oval ports. The "closed" chamber makes things a LITTLE tougher, but not a big deal. Icon makes a nice replacement piston that's lighter than the Speed Pro, and you can still machine the dome to "fit". Both the Icon and Speed Pro are readily available and up to the task.

We install the 2.190/1.88" valves in the oval port heads all the time. A little "blending" in the bowls is all that's really needed, and they can "feed" a 396 well over 7,000.

So, yes, 396 can be a very potent street engine. And no, you don't need the monster money parts to do it.

BTW: All 366s, 396s and 427s used the 6223 crankshaft. Good forging. I don't believe you need a 4-bolt until power exceeds 600 HP or RPM exceeds 7,500. Then, installing splayed-bolt caps to your existing block would be infinitely more desirable than trying to find a 375 or 425 HP block...

Jim

03-07-2013 05:04 PM

ap72

It's be a lot cheper to just buy a good 454 core and do a cam and intake swap. Just because you have something g doesn't mean it's a better idea.

Or a stock 396 2 bolt main 325 HP, forged stock pistons & rods, the heads you have and supercharge it at about 7 to 10 pounds boost with a mild force induction cam 500 hp is easy and street able max RPM around 5500 a lot cheaper!! Or spray it that's even cheaper.

500 HP out of a normally aspirated single carb 396 325 HP engine with stock bore calls for very high compression and big money! The 65 396 was called the fat block because of the cylinder wall thickness and could be bored to extremes so if that's the block you have you have a lot to work with, 4 bolt mains your best choice , the 2 bolt mains limit your build depends where your money runs out " MONEY = HP, TORQUE, and SPEED"Cylinder-Head Flow-Bench Database
GM 702 Iron Oval Port an early 396ci and 427ci closed-chamber head used only in ’65 and ’66. This head virtually clones the GM 290’s flow numbers. While the 049 head flows much better the 049s would drop compression two full points. The best set up here is to either give up some power and use the GM 702 head you don't lose much or go with the better GM 049 head and Open chamber pistons to match.

GM 049 Iron Oval Port This Open chamber oval-port head saw use in a number of 402ci to 454ci big blocks from ’73-’84. Of the three stock iron oval-port this one was the strongest. Again, like other production heads, if horsepower is your goal, larger valves are the way with these heads

I believe it's a 325 HP motor. I know about the groove in the cam. So it's a no go then? The heads don't such enough air? Too much machine work: hardened seats, spring pockets, bigger valves and eye brow and valve shroud clearance? No comments on the cams? Can very mild port work make these heads flow 300cfm @.600 in 20inches? No bigger intake valves? What say you about the cams?

03-07-2013 11:21 AM

vinniekq2

A Side Note:
The correct cam bearings for the engine you have is very impotent some take a grooved rear cam bearing #396 Clevite SH615S 65-66 only!!!
Clevite SH616S 67-93 396-427.

Jester
good thing to remember

03-07-2013 10:40 AM

painted jester

Which engine do you have 396-cid 425-hp with 11.0:1 compression ratio? or the 396 375 hp?, 396 325 HP? etc, piston ranges were from 9:1 to 11:1 forged! What pistons do you have?

four-bolt main caps?

The 1965 396/425 HP,

The 396 was offered in several configurations and produced different horsepower and torque ratings, depending on its intended application.

The 396 with a 10.25 compression ratio produced 325 horsepower at 4,800 rpm and 410 ft. lbs. of torque at 3,200 rpm.

The Z16 performance 396 with a 11.00 compression ratio produced 375 horsepower at 6,500 rpm and 420 ft. lbs. of torque at 3,600 rpm.

The 396 with a 11.00 compression ratio produced 360 horsepower at 5,200 rpm and 420 ft. lbs. of torque at 3,600 rpm.

A Side Note:
The correct cam bearings for the engine you have is very impotent some take a grooved rear cam bearing #396 Clevite SH615S 65-66 only!!!
Clevite SH616S 67-93 396-427.

Jester

03-07-2013 08:50 AM

vinniekq2

consider a Z-33 cam from Isky,or something similar
its .560 lift,108º lobe center and 250º duration @.050
Obviously you could spend more and get a roller cam and custom pistons

My street 454 I used open chambers and a Z-55 and it worked quite well.I picked up 4/10s when I took off the performer and put on an oval vic jr

03-07-2013 04:55 AM

BOBCRMAN@aol.com

The 702 heads are not real good flow heads. Will require much labor $$$ to work. Hard seats with 2.19-1.88" valves will help flow and streetability. But, The small chambers, which you need on a 396, shroud the valves. Also will need valve spring pocket work to install springs for roller lift specs $$$.
Add the basic machine work $$$ and parts to make these old heads usable and you have a major investment in mediocre heads.

+.300 lifters are for later blocks. Go with steel retainers.

Then you get into pistons. Only basic rebuilders stuff is stocked or even available by most warehouses. Not suitable for your intended use. So unless you want to custom order some forgings. $700.00+ your other option is using Keith Black hypers. Also usually not stocked by warehouses.

I am going thru a situation with a customer right now.
He is on a modest budget and insists on using a 402 block and crank. Plus his buddies keep advising him on this build.
He had a good 454 short block but traded it for some reason. Now he has to pay the small bore BBC penalty.

Here is what he has to work with.
402+030 2-bolt block.
cast crank
oval port 112 cc heads.

Problem 1= because of cost and availability, he had to go with replacement pistons, universal dome, .020 short.
Problem 2- I advisd him to at least install aftermkt valves and hard exh seats in heads and 2.19" intakes. His buddies say no. Not needed on small engine.. So it's basic work plus trying to find usable springs/retainers/seals for the cam he insists on. A .700" lift 108 cl. Roller.
Problem 3= Valve to piston clearance with stock design piston. Glad I'm not assembling this engine.

I could go on for a couple of pages but engine people will see what this is going to turn out as..
Just let your "expert" buddies help you with your engine. The guy with 40 + years at the machine shop don't know crap!

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